Commercial gas turbines are known in the art for generating power. A typical gas turbine used to generate electrical power includes an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. Ambient air may be supplied to the compressor, and rotating blades and stationary vanes in the compressor progressively impart kinetic energy to the working fluid (air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows through one or more nozzles into a combustion chamber in each combustor where the compressed working fluid mixes with fuel and ignites to generate combustion gases having a high temperature and pressure. The combustion gases expand in the turbine to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
The combustion gases exiting the turbine include varying amounts of nitrous oxides, carbon monoxide, unburned hydrocarbons, and other undesirable emissions, with the actual amount of each emission dependent on design and operating parameters. For example, the design length of the combustor directly effects the amount of time that the fuel-air mixture remains in the combustor. A longer residence time of the fuel-air mixture in the combustor generally increases the nitrous oxide levels, while a shorter residence time of the fuel-air mixture in the combustor generally increases the carbon monoxide and unburned hydrocarbon levels. Similarly, the operating level of the combustor directly influences the emissions content on the combustion gases. Specifically, higher combustion gas temperatures associated with higher power operations generally increase the nitrous oxide levels, while lower combustion gas temperatures associated with lower fuel-air mixtures and/or turndown operations generally increase the carbon monoxide and unburned hydrocarbon levels. Therefore, continued improvements in the combustor designs and methods for supplying fuel to the combustor would be useful to reducing undesirable emissions in the combustion gases.